As is known, organic and inorganic deposits are formed on the surfaces of the contact lenses, and microorganisms as well as fungi also collect there. The organic deposits are parts of the lacrimal fluid such as proteins, mucines and lipids. The inorganic deposits (metal, iron, rust) are due to environmental conditions (air pollution, road dust, metal abrasives). Additional inorganic deposits are those of calcium salts which are also called hard water deposits. They are formed when flushing the lenses with tap water or due to a change of the pH value of the lacrimal fluid, e.g. due to medicaments or physiological influences. The microorganisms (bacteria, virus) and fungi belong to the normal microflora of the conjuctiva, the conjuctive sac and the lacrimal ducts. The normal microflora change as soon as the balance of the microflora becomes disturbed, be it due to germ transfer via the hands, improper cleaning and desinfection, illness or metabolic disturbances (diabetic) of the lens wearer or due to contact of the lenses with the environment. In addition it is known that the contact lenses, in the course of their use, are subjected to changes, such as changes and damage of their material. The changes of the material, e.g. discolorations, are based on environmental influences, e.g. cigarette smoke, colored vapors, cosmetics, or stains transferred from storage containers. Damage may be in form of hairline cracks, abrasions, scratches, marginal fractures or breaks, and due to improper handling of the contact lenses.
These changes of the contact lenses listed above result in various complications for the user or wearer such as e.g. an intolerability against the contact lenses so that they cannot be worn anymore. Also acute medical conditions, such as development of diseases by infection (to be observed particularly on lenses worn during extended periods) or chronic irritations as a gigantopapillary conjuctivitis, can be observed; they are somewhat less numerous but are at the center of medical treatments. Since the contact lenses are subjected to many influences adversely affecting their wearing quality and optical characteristics, regular inspections by the person adapting them (ophthalmologist, optician) to the wearer as well as by the wearer must be provided. Each wearer of contact lenses is instructed to clean them daily if possible. The sooner the cleaning is effected, the greater is the success. Various cleaning methods are in use such as e.g. chemical, thermic, encymatic, mechanical or ultrasonic treatments. In order to carry out the inspection, use of the following methods is made:
Contact lens viewing on the eye with a slit lamp (binocular microscope);
contact lens viewing with the lens held on the finger or placed in a transparent container filled with fluid, by using the naked eye and the slit lamp;
contact lens viewing in black field illumination by using a binocular microscope.
Such inspections are complicated, can only be carried out by the ophthalmologist or optician or they provide insufficient information.